diff --git a/src/handlers/AltClickHandler.ts b/src/handlers/AltClickHandler.ts
index 85465272..7f2e4f05 100644
--- a/src/handlers/AltClickHandler.ts
+++ b/src/handlers/AltClickHandler.ts
@@ -28,7 +28,7 @@ export class AltClickHandler {
     this._startCol = this._terminal.buffer.x;
     this._startRow = this._terminal.buffer.y;
 
-    [this._endCol, this._endRow] = this._terminal.mouseHelper.getCoords(
+    let coordinates = this._terminal.mouseHelper.getCoords(
       this._mouseEvent,
       this._terminal.element,
       this._terminal.charMeasure,
@@ -36,16 +36,20 @@ export class AltClickHandler {
       this._terminal.cols,
       this._terminal.rows,
       false
-    ).map((coordinate: number) => {
-      return coordinate - 1;
-    });
+    );
+
+    if (coordinates) {
+      [this._endCol, this._endRow] = coordinates.map((coordinate: number) => {
+        return coordinate - 1;
+      });
+    }
   }
 
   /**
    * Writes the escape sequences of arrows to the terminal
    */
   public move(): void {
-    if (this._mouseEvent.altKey) {
+    if (this._mouseEvent.altKey && this._endCol !== undefined && this._endRow !== undefined) {
       this._terminal.send(this._arrowSequences());
     }
   }